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Unix supports most of the popular sound cards. If you don't have a sound card, you can still get a degree of sound support from your humble PC speaker. In this article, I will examine one way of doing this.
PC-Speaker is a driver for the modest sound output device that comes as standard with most (all?) IBM PC clones. it involves installing the driver as part of the kernel, or as a loadable module. Either way, the kernel needs to be changed. It comes with a small set of programs to use with it. These compiled without trouble on my system.
The driver comes as a patch file, which must be applied against the Unix source directory (/usr/src/linux). When make config is run after this, you will be asked whether you want PC Speaker support - say yes! A short "make depend; make clean; make zImage" later, and your new kernel is ready. The patches to the source include some header files for /usr/include/sys, which are necessary to make the utilities that accompany it.
The driver supports the following devices :
/dev/pcsp - the raw data device
/dev/pcaudio - the SUN-audio device
/dev/pcmixer - the mixer-device
I have only the /dev/pcsp defined on my machine, like so:
crw—w—w- 1 root root 13, 3 Aug 27 20:25 /dev/pcsp
Having installed the driver, and devices, there is the matter
of configuration.
This program Sets options for the PC speaker. It should be used to configure your /dev/pcsp at system startup or for testing new devices.
You can 'assign' an output-device to /dev/pcsp, using the pcsel program. The supported output devices are as follows:
Stereo-on-One (designed by Mark J. Cox), this is auto-detected during
kernel startup and selected by default
PC-Speaker is selected if no Stereo-on-One was found
Mono DAC on one lp-port
Stereo DAC on two lp-ports
$ pcsel —help
pcsel 0.9c (12 Oct 95)
Usage: pcsel [OPTIONS]
-V —version output version information and exit -d —device=DEVICE set the output-device -p —port=PORT the lp port to use (0-2) for single DAC -r —right-port=PORT the lp port for the right DAC -l —left-port=PORT the lp port for the left DAC -b —realspeed=SPEED set the real sampling rate for PC-Speaker -e —emulation=on|off enables or diables the 16bit stereo emulation -s —speed=SPEED set the sampling rate -M —mono set mono -S —stereo set stereo if possible -v —volume=VOLUME set the volume for PC-Speaker -h —help display this help and exit
supported devices : 'Sto1' : Stereo-on-One 'DACm' : Mono DAC 'DACs' : Stereo DAC 'PCSP' : PC-Speaker
Without options pcsel reports the actual output-device and its parameters.
$ pcsel
PCSP driver version 1.0
Actual PCSP output device: PC-Speaker
Volume : 100 %, real samplerate : 18356 Hz
Maximum Samplerate is 51877 Hz
16bit Stereo Emulation enabled
These programs can be used for recording and playing:
CREATIVE LABS VOICE files
MICROSOFT WAVE file
raw audio data.
Both programs accept the same options:
$ vplay —help
vplay 1.2 (12 Oct 95)
Usage: vplay [OPTIONS] [file ...]
-V —version output version information and exit -S —stereo stereo output (default is mono) -s —speed=SPEED sets the samplerate (default is 8000 Hz) -t —timelimit=SEC sets the recording time in seconds -b —samplesize=BITS sets the sample size (default is 8 bit) -o —device=DEVICE changes the audio device (default is /dev/dsp) -v —voc record a CREATIVE LABS VOICE file (default) -w —wave record a MICROSOFT WAVE file -r —raw record raw data without header -q —quiet quiet mode -d —verbose show verbose informations -h —help display this help and exit
OK, confession time. The only real reason I had for adding this driver to my kernel was so that I could have sound effects in Doom! Here is another, trivial, example, of what you can do. I have a directory of .wav and .au files. Here is a shell script, called from my .profile, that plays one of these at random each time I login.
#!/bin/sh
#random-sound.sh: play a random file from the sounds directory
export count="`ls sounds/*|wc -l|sed 's/ //"
export count=`expr $count + 0`'
`(1>/dev/null 2>&1 vplay `echo sounds/*|awk 'BEGIN{srand()}{x=1+int(rand()*number);print $x}' number=$count`) &'
The latest version will be at ftp.informatik.hu-berlin.de, in the directory /pub/os/linux/hu-sound/pcsnd* (where * represents the latest version number).
This is neat bit of software that makes good use of the basic PC speaker. You will get plenty of interference if your computer is "digitally noisy". It is unlikely to be made part of the standard kernel; the author, Michael Beck (beck@dgroup.de), says that one of the reasons is that it interferes with the Linux clock. I hadn't noticed this myself, but then my clock is re-synched with my ISPs four times a day. The distribution comes with a file, that describes how to build your own sound output devices - so that you PC can connect to your amp, for example. I may try one of these projects in future - watch this space!
Paul Dunne 1997
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Last changed: Sun Mar 3 00:50:18 CET 2019
